Minimum fluid circuit breaker including stroke-dependent injection of quenching fluid into switch contact chamber

ABSTRACT

A minimum-fluid circuit-breaker includes a quenching chamber in which the fixed and movable contacts are located, a pump of the piston-cylinder type, the piston being rigidly connected to the movable contact and serving to force arc-quenching fluid from the pump cylinder into a pressure chamber and thence from the latter through non-return valving into the quenching chamber to facilitate arc extinction as the contacts disengage. The rate-offlow of the arc quenching fluid into the quenching chamber is varied during movement of the pump piston. By utilizing a row of bypass ports in the pump cylinder which are progressively cut out by the piston during its movement in the contact opening direction, the flow rate is progressively increased. By utilizing a double concentric pump piston arrangement both pistons act conjointly on the fluid during the initial part of the piston movement to provide a high flow rate while thereafter only the smaller of the two pistons is effective thus providing a correspondingly lower flow rate. When the contacts reclose, the pressure chamber and pump cylinder refill with fresh fluid from a reservoir.

United States Patent [191 Wehrii 1Marci1 2c, 1973 MINIMUM FLUID CIRCUIT BREAKER INCLUDING STROKE-DEPENDENT INJECTION OF QUENCHING FLUID INTO SWITCH CONTACT CHAMBER Robert Wehrli, Nurensdorf, Switzerland Aktiengosellschaft Brown, Boveri 81 Cie, Baden, Switzerland Filed: May 10,1971

Appl, 190.; 141,799

[75] Inventor:

[73] Assignee:

[56] References Cited UNITED STATES PATENTS Leeds et a1. ..200/148 A Buechner ..200/ 148 A FOREIGN PATENTS OR APPLICATIONS Primary Examiner-Robert S. Macon Attorney-Pierce, Scheffler & Parker [57] ABSTRACT A minimum-fluid circuit-breaker includes a quenching chamber in which the fixed and movable contacts are located, a pump of the piston-cylinder type, the piston being rigidly connected to the movable contact and serving to force arc-quenching fluid from the pump cylinder into a pressure chamber and thence from the latter through non-retum valving into the quenching chamber'to facilitate arc extinction as the contacts disengage. The rate-of-flow of the arc quenching fluid into the quenching chamber is varied during movement of the pump piston. By utilizing a row of bypass ports in the pump cylinder which are progressively cut out by the piston during its movement in the contact opening direction, the flow rate is progressively increased. By utilizing a double concentric pump piston arrangement both pistons act conjointly on the fluid during the initial part of the piston movement to provide a high flow rate while thereafter only the smaller of the two pistons is effective thus providing a correspondingly lower flow rate. When the contacts reclose, the pressure chamber and pump cylinder refill with fresh fluid from a reservoir.

1 Claim, 5 Drawing Figures PATENTEDHARZOIQB SHEET 10F 3 Figia PATENTEDmzoms SHEET 2 OF 3 Fig.2a

Fig.2

MINIMUM FLUID CIRCUIT BREAKER INCLUDING STROKE-DEPENDENT INJECTION OF QUENCIIING FLUID INTO SWITCH CONTACT CHAMBER The present invention relates to a minimum-fluid circuit-breaker with supplementary injection of arcquenching fluid into the quenching chamber, employing a piston coupled to a contact rod and moving in a pump cylinder and, connected to the pump cylinder, a reservoir into which quenching fluid is conveyed during the switching-in movement of the contacts, and to which the fluid returns by way of the quenching chamber during the contact-opening movement.

The technique is already well known whereby the moving contact of a circuit-breaker is rigidly connected to a piston which, during the contact-opening movement, generates a jet of quenching fluid which is led along the moving contact and directed at the fixed contact.

It is also established practice to link the pump cylinder to a reservoir into which quenching fluid is conveyed from an intermediate chamber during the contact-closing movement, while during the contactopening process the fluid returns to the intermediate chamber by way of the quenching chamber and a space between the quenching chamber and an insulator, and also to locate valves between the reservoir and intermediate chamber in order to prevent reversed flow of the quenching fluid.

The disadvantage, however, is that no overpressure, or only very little, can be created in the spark gap, and even when the self induced transverse blast is reinforced by quenching fluid injected under pressure into the quenching chamber from a separate source, it has been possible hitherto to achieve only a uniform flow rate of quenching fluid injected into the quenching chamber throughout the entire contact-opening process.

The purpose of the present invention is to provide an arrangement which does not exhibit the disadvantages and shortcomings of the known solutions.

This purpose is achieved in that the flow rate of quenching fluid conveyed into the quenching chamber by the pump piston rigidly coupled to the contact rod is varied independently during the course of the opening process.

The effect of the arrangement in accordance with the invention is not only that the flow rate of the quenching fluid conveyed during the opening movement of the contact rod varies, but also that the pressure of the quenching fluid injected into the quenching chamber varies according to the position of the 'pump piston rigidly coupled to the contact rod.

In a specially advantageous form of the invention, bypass ports are provided between the pump cylinder and an intermediate chamber. It is recommended that these bypass ports should be of different cross-section areas. The effect of this arrangement is that the flow rate of quenching fluid propelled by the pump piston and injected into the quenching chamber is lower at the beginning of the contact opening process than at the end.

In accordance with another version of the invention, the pump piston rigidly coupled to the contact rod is constructed in the form of a double piston. With this arrangement, the flow rate of quenching fluid propelled by the main piston, in which the smaller piston is seated, at the beginning of the contact opening process is relatively high, whereas subsequently, after the main piston has been restrained by a stop located in the pump cylinder, the flow rate of quenching fluid injected into the quenching chamber by the continued movement of the small piston is lower.

Various embodiments of the improved circuitbreaker in accordance with the invention are shown schematically in the accompanying drawings wherein:

FIG. 1 is a cross-section through the pump arrangement of a minimum-fluid circuit-breaker;

FIG. 1a is a cross-section through the pump cylinder and intermediate chamber;

FIG. 2 is a longitudinal section through the minimum-fluid circuit-breaker;

FIG. 2a is a longitudinal section, at to the section of FIG. 2, through the minimum-fluid circuit-breaker; and

FIG. 3 is a longitudinal section through a modified pump arrangement with a double piston for a minimum-fluid circuit-breaker.

In the various views the same components are denoted by the same reference numbers.

With reference now to FIG. 1 there is shown a minimum-fluid circuit-breaker with insulator housing 1 containing quenching-medium pump. A pump piston 2 is rigidly connected to a contact rod 3 and moves up and down in a pump cylinder 4 with the closing and opening movements, respectively, of contact rod 3. At one side of pump cylinder 4 are bypass ports 5 which are of different cross-section areas. Bypass ports 5 provide access to an intermediate chamber 6, while on the opposite side of pump cylinder 4 a port 7 provides access to a pressure chamber 8 which, in turn is connected at the bottom via a non-return valve 9 and connecting duct 10 to the oil reservoir, and at the top has a port 11 with valve 12 providing access to quenching chamber 13. The intermediate chamber 6 is connected by way of ports 14 and 15 to a low-pressure chamber 16, which also leads to the quenching-medium reservoir.

In FIG. 2 the insulator housing of the minimum-fluid circuit-breaker is again denoted 1; contact rod 3, rigidly coupled to pump piston 2, is here shown in the open position.

The opening movement is represented in FIG. 2a. Pump piston 2 is with one side just covering one of the bypass ports 5 and so controls with its length of stroke the flow rate of quenching fluid injected into quenching chamber 13 by way of pressure chamber 8.

In FIG. 3 the contact rod 3 is coupled to a double piston consisting of a main piston 17 and a secondary piston 18. The double piston, composed of main piston 17 and secondary piston 18, moves up and down in a pump cylinder 4 with the closing and opening movements, respectively, of contact rod 3.

The main piston 17 has a recess 20 which accommodates the secondary piston 18 when the contact rod 3 is in the raised position. Pump cylinder 4, together with stop 19, also has a connecting port 7 which leads to pressure chamber 8.

All design features not essential to an understanding of the invention, for example, the actuating mechanism of the minimum-fluid circuit-breaker are well known and have have been omitted from FIG. 1 to 3 in the interest of simplicity.

Operation of the arrangement according to the invention can be described in the following manner.

When, during the opening process, contact rod 3 and the pump piston 2 rigidly connected to it move downwards, the quenching fluid in pump cylinder 4, in the intermediate chamber 6 and in the pressure chamber 8 is compressed by pump piston 2, whereupon part of the fluid escapes through bypass ports 5, intermediate chamber 6 and ports 14 and 15 into the lowpressure chamber 16, while the remainder of the quenching fluid flows through connecting port 7 into the high-pressure chamber 8 and is forced through port 11, hitherto closed by valve 12, into the quenching chamber 13. Since the downward movement of pump piston 2 creates a corresponding increase of pressure in pressure chamber 8, non-return valve 9 is closed. During the contact-closing process, quenching fluid flows from the oil reservoir through connecting duct 10 into the pressure chamber 8, pump cylinder 4 and intermediate chamber 6.

Since quenching fluid overflows through bypass ports 5 into intermediate chamber 6 and low-pressure chamber 16, the flow rate of quenching fluid injected into quenching chamber 13 is lower at the beginning of the contact-opening process than towards the end of the process, because then most of the bypass ports 5 are covered by the descending pump piston 2 and the quantity of quenching fluid in pump cylinder 4 can pass only through connecting port 7 into pressure chamber 8 and from there through the open valve 12 into quenching chamber 13.

If a double piston is used, this is fully raised when the circuit-breaker is in the closed position. During the opening process, contact rod 3, together with the do'uble piston consisting of main piston 17 and secondary piston 18, moves downwards and thus at first forces the quantity of quenching fluid above stop 19 through connecting port 7 into pressure chamber 8 and thence into quenching chamber 13. When the main piston 17 reaches stop 19, it is restrained by this, and secondary piston 18 continues to move downwards with contact 3,

whereupon the remaining quantity of quenching fluid also passes through port 7 into pressure chamber 8. Consequently, the flow rate of quenching fluid injected into the quenching chamber is at first higher, and at the end of the opening process lower, corresponding to the smaller cross-section area of secondary piston 18.

In the embodiment of FIG. 3, during the first phase of the movement of the double piston, the piston components 17,18 move together by reason of a releasable coupling such as a conventional spring loaded ball detent mechanism. When the main piston 17 is stopped, the coupling between the two pistons releases thus permitting the secondary piston to continue its downward movement.

The flow direction of the quenching fluid is indicated by arrows in the various views.

I claim:

1. In a minimum-fluid circuit-breaker, the combination comprising an arc-quenching chamber in which the fixed and movable contact members are located, a

pump of the piston-cylinder type, and a pressure chamber communlcatmg with sai pump cylinder and also with said arc-quenching chamber, said pump cylinder and pressure chamber being filled with the arc-quenching fluid from a reservoir when said contact members are in the closed position and which fluid is injected into said arc-quenching chamber by the pump piston when said movable contact member disengages from said fixed contact member, said pump piston being actuated by and controlled in accordance with the stroke of said movable contact member and being constituted by two concentric and separable piston components, said piston components being united and acting conjointly on said arc-quenching fluid in said pump cylinder during the initial part of the stroke of said movable contact member in the contact opening direction thereby to provide a high fluid flow rate, and stop means then engageable with the larger of said two piston components whereby said piston components are thereafter separated and only the smaller of the two piston components continues its movement within said cylinder thereby to provide a lower fluid flow rate from said cylinder and pressure chamber into said arcquenching chamber.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent 3,721,787 Dated March 20; 197? Invent ROBEKE WEHRLI It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Foreign Application Priority Data May 22, 1970 Switzerland,..,..,. 7832/70 Signed and sealed this 17th day of September 1974.

(SEAL) Atteet:

McCOY Mm GIBSON JR. C. MARSHALL DANN Commissioner of Patents Attesting Officer 'IORM po'mm H0439) USCOMM-DC 60376-P69 LLSv GOVERNMENT PRINTING OFFICE: 1989 0-366-334,

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent 721,787 Dated March 20 1W2 Invent ROBERT WEHRLI It is certified that error appears in the above-idehtified patent and that said Letters Patent are hereby corrected as shown below:

Foreign Application Priority Data May 22, 1970 Switzerland........ 7832/70 (SEAL) Attest:

MCCOY Mu. GIBSON JR. Attesting Officer C. MARSHALL DANN Commissioner of Patents FORM P Q-1050 (10-69) USCOMM DC 6O376 P69 u.s. covznymsm PRINTING OFFICE: 1959 o-3ss-3a4. 

1. In a minimum-fluid circuit-breaker, the combination comprising an arc-quenching chamber in which the fixed and movable contact members are located, a pump of the pistoncylinder type, and a pressure chamber communicating with said pump cylinder and also with said arc-quenching chamber, said pump cylinder and pressure chamber being filled with the arc-quenching fluid from a reservoir when said contact members are in the closed position and which fluid is injected into said arcquenching chamber by the pump piston when said movable contact member disengages from said fixed contact member, said pump piston being actuated by and controlled in accordance with the stroke of said movable contact member and being constituted by two concentric and separable piston components, said piston components being united and acting conjointly on said arcquenching fluid in said pump cylinder during the initial part of the stroke of said movable contact member in the contact opening direction thereby to provide a high fluid flow ratE, and stop means then engageable with the larger of said two piston components whereby said piston components are thereafter separated and only the smaller of the two piston components continues its movement within said cylinder thereby to provide a lower fluid flow rate from said cylinder and pressure chamber into said arc-quenching chamber. 